1. Field of the Invention
The present invention relates to a printed antenna, which has an ultra wide-band (“UWB”) frequency range. The ultra wideband antenna is loaded on UWB wireless devices for its use. Therefore, it is required to be low and small profile, light weight and low cost. Moreover, the characteristics of ultra wideband antenna have to be constant gain and omni-directional patterns.
2. Description of the Related Art
Growing use of wireless communication devices has forced the need of large bandwidth, and large bit-rates, such as bit-rates of several hundred Mbps. It requires an antenna having excellent characteristics in the range of ultra wideband frequency. Further the antenna has to be small profile, light weight and low cost.
FIG. 14A and FIG. 14B show a prior art of an example of wide frequency band patch antenna, that is a bow-tie type patch antenna. FIG. 14A shows a cross sectional view of the antenna, and FIG. 14B shows a top view of same. In FIG. 14A and FIG. 14B, a substrate 20 is composed of dielectric material such as FR4. A patch 21 has a figure like a bow-tie. The patch 21 is made of metal as copper. A ground plate 22 of copper is provided on the back surface of the substrate. The patch 21 is connected to a line of coaxial cable which penetrates through the substrate 20. The shield of the coaxial line is connected to the ground plate 22.
The prior art of a printed bow-tie type antenna shown in FIG. 14A and FIG. 14B does not have the wide frequency range such as the ultra wide frequency, thus it is unsuitable to cover the ultra wideband frequency range. Several designs to make the patch antenna wide band have been reported, such as noted below in references 1–6. Their frequency range, however, is not be able to cover the ultra wideband communication frequency range of 3.1–10.6 GHz.
As mentioned above the prior art printed antenna have not satisfied the practical use of the ultra wideband communication devices so far. Because it is very difficult to make the wideband printed antenna having good frequency characteristics of the ultra wideband communication.
The following are references to the related art:
1. G. Kumar and K. C. Gupta, “Directly coupled multi resonator wide-band microstrip antenna,” IEEE Trans. Antennas Propagation, vol. 33, pp. 588–593, June 1985.
2. K. L. Wong and W. S. Hsu, “Broadband triangular microstrip antenna with U-shaped slot,” Elec. Lett., vol. 33, pp. 2085–2087, 1997.
3. F. Yang, X. X. Zhang, X. Ye, Y Rahmat-Samii, “Wide-band E-shaped patch antenna for wireless communication,” IEEE Trans. Antennas Propagation, vol. 49, pp. 1094–1100, July 2001.
4. A. K. Shackelford, K. F. Lee, and K. M. Luk, “Design of small-size wide-bandwidth microstrip-patch antenna,” IEEE Antennas Propagation Magz., vol. 44, pp. 75–83, February 2003.
5. J. Y Chiou, J. Y. Sze, K. L. Wong, “A broad-band CPW-fed strip-loaded square slot antenna,” IEEE Trans. Antennas Propagation, vol. 51, pp. 719–721, April 2003.
6. N. Herscovici, Z. Sipus, and D. Bonefacic, “Circularly polarized single-fed wide-band microstrip patch,” IEEE Trans. Antennas Propagation, vol. 51, pp. 1277–1280, June 2003.